All petrol caps EXCEPT the CA screw on caps are vented at the cap to allow fuel flow. This may or may not be part of what some of you are seeing. The CA caps are sealed to prevent HC from escaping from the tanks. CA is the only place in the world with this requirement and I am surprised. These tanks are vented into a canister with activated charcoal in them. The charcoal absorbs the vapors. When the bike runs it draws a small amount of air through the canister which purges it. There are no negative performance problems with it. They look unsightly but that can be improved upon. For my money it is a good device.

Some riders had mentioned that their Cork Gaskets swell up or became mushy. Just beware to find the right material.

---------------------------------------------------------------------------This is from an old Post "Do it yourself Gas Cap Gasket" bullethead63 Grand Gearhead Posts: 696Re: Do it yourself Gas Cap Gasket (or Petrol Cap, if you wanna be fancy)« Reply #10 on: November 04, 2010, 10:18:11 AM » --------------------------------------------------------------------------------After about a week,my new gasket has gotten a little mushy,and swollen...if you're going to use one of these for a petrol tank cap,keep a spare in your tool box,and switch them out with every fill up...that's what I had to do this morning...

walken4life Scooter Posts: 50Re: Do it yourself Gas Cap Gasket (or Petrol Cap, if you wanna be fancy)« Reply #11 on: November 05, 2010, 08:40:25 AM » --------------------------------------------------------------------------------That's sad. Mine seemed ok last fillup but I will check it again when I do the final fill up before winter storage in the next few days. Thanks for the update.« Last Edit: November 14, 2010, 08:02:45 AM by walken4life »

+1. That's why you should look for fuel resistant cork gasket material at an auto shop, not craft supply stuff. A whole roll cost me about $6 I think. Same goes for the o-ring solution, fuel resistant or it will turn to mush.

I use plain old 2mm cork sheet which I buy in bulk (for my business) from the sawmill. It works fine. I did grease it at first, but only the once, and it's still good after a year or so. Perhaps it just happens to be gasket grade - it's fairly dense. I have seen some poorer quality stuff around, so I guess that'll be the craft shop stuff.

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2010 Royal Enfield Electra (G5) - fully Hitchcocked

2004 Kawasaki W650 (gone but not forgotten...)~ the best british bike they never made ~

Although some of the colors of these materials are the same, the colors can indicate if you've got the right material for others.There are no hard and fast rules about these colors so use them as a general guide.

For instance, Silicone, which is very poor with gasoline is usually orange.Fluoro-silicone, which is excellent with gasoline is usually blueEuropean Viton is usually green but American Viton is usually brown.Buna-N (Nitrile) is often grayNeoprene is usually blackColor Kalrez (Perfluoroelastomer) EXPENSIVE. It is so expensive that we used it in jet engines only when nothing else would do.

On my 2010 Bullet C5 (with under 1000 miles), I smell gas fumes more often than I anticipated.

And I had this happen: I filled the tank at night in cold winter weather, then parked the bike on the side stand in a warm garage. Overnight, due to expansion, gas dribbled over the side onto the floor.

Since then, in the warm garage I always park on the center stand. And I ordered a roll of "cork gasket material" from an Amazon vendor, which came last night -- when the snow clears, I'll cut a ring of it out and try it in the tank.